Reconsider setting engines.yarn to an invalid version

[markandrus]

Please reconsider setting engines.yarn to an invalid version and perhaps instead merge #11. Although the intention for setting engines.yarn was made clear in #7 (comment) and may be appropriate for an application or an internal libary, it's a problematic choice for external libraries, where consumers should be free to use just about any package manager they choose.

This invalid engines.yarn has been removed in packages like mixmaxhq/rollup-plugin-root-import (see mixmaxhq/rollup-plugin-root-import#10) and hopefully soon honeycombio/libhoney-js (see honeycombio/libhoney-js#169). Making this change in deyarn (or perhaps having some configuration/warning around it) will help prevent future issues.